1. Field of the Invention
The present invention relates to a silicon wafer production process and a silicon wafer.
2. Description of the Related Art
In recent years, ever since grown-in defects were demonstrated to cause deterioration of Gate Oxide Integrity (GOI) in silicon wafers, numerous attempts have been made to decrease these grown-in defects.
In particular, technology for growing near-perfect crystals almost free of defects in which v/G (a ratio of ingot pulling velocity (v) to temperature gradient in the ingot near the interface between the ingot and a melt (G)) is controlled when pulling out the single crystal ingot, has been applied practically to the production process of growing near-perfect silicon single crystals.
Silicon wafers free of crystal defects such as Crystal Originated Particle (COP) defects, void defects such as Flow Pattern Defects (FPDs) or the like, and dislocations and the like are used practically as silicon wafers of near-perfect crystals.
Also, as a wafer processing technology to obtain the silicon wafer having extremely satisfactory GOI by eliminating bulk defects (such as COP defects and FPDs) on the surface, technology has been proposed to heat-treat a silicon wafer in an argon or other inert gas atmosphere or in hydrogen by using an electric furnace.
In addition, in recent years, technology for enhancing oxygen precipitation has been widely proposed to form vacancies in silicon crystals by heat-treating a silicon wafer with rapid heat process to high temperature and rapid cool process. For example, a process has been proposed to increase amounts of oxygen precipitation by treating the silicon wafer with rapid heating and cooling treatment (Rapid Thermal Annealing: RTA) in nitrogen or oxygen.
However, although the aforementioned near-perfect crystal silicon wafer is basically free of COP defects and dislocations, residual crystal defects such as oxidation induced stacking fault nuclei (OSF nuclei) are formed due to slight changes in growth conditions, thereby resulting in the problem of the residual crystal defects causing deterioration of GOI.
Also, residual defects resulting from the wafer processing process have been determined to cause deterioration of GOI.
In the case in which beat-treating a silicon wafer in argon or other inert atmosphere or hydrogen, there is the disadvantage of the effects being limited to the vicinity of the surface. In the case of normally used wafers having COP defects, since the internal COP defects remain even after heat treatment, there is the problem of these residual COP defects having a detrimental effect on device characteristics. In the case in which a silicon wafer is heated at high temperature by using an electric furnace, a stress occurs in wafers, in particular in wafers measuring 300 mm in diameter, a large stress occurs, and also problems of slippage occur, thereby resulting in concerns about detrimental effect on their application.
In the case in which heat-treating a silicon wafer with RTA treatment in nitrogen or oxygen, since it is necessary to remove the nitride film or oxide film formed on the surface by machine work or chemical treatment, it couled lead to cause deterioration of GOI. Therefore, in Japanese Unexamined Patent Publication No. H11-135514, as a technology that does not involve the formation of a nitride film or a oxide film on the surface and also improves surface characteristics, a process is proposed to heat-treat a silicon wafer with RTA treatment in hydrogen or argon containing hydrogen. In this process, although the problem of GOI deterioration resulting from machine work is resolved, in the case of normally used wafers having COP defects, even in the case of small COP defects in the manner of nitrogen-doped crystals, the COP defects are unable to be eliminated in a short period of time, thereby preventing improvement of GOI deterioration caused by the presence of COP defects in bulk.